So-called "molly" bolts have been used in the past. These molly bolts are expandible bolts having a split sheath-like sleeve threaded at one end. When the bolt is inserted snugly into masonary, for example, the turning of the bolt draws the ends of the sheet together thus spreading the sides of the sheath to maintain the bolt firmly in place.
Various other types of bolts have used features similar to the molly bolt. In such a bolt, the bolt is inserted through one or two aligned openings with a threaded stem being used to expand the prongs which hold the bolt in place.
In the manufacture of refrigerated trailers, for example, it is often necessary to utilize hundreds of rivets to secure two structures to each other such as for example a corner molding to join adjacent panels.
When such a larger number of rivets are involved, it is impractical to utilize threaded rivets to cause expansion of sheaths within openings because the time involved in such operations would be excessive and would greatly add to the overall cost of the trailers involved.
Also used heretofore have been rivets in refrigerated trailers for insertion into openings between two structures. Instead of using threaded portions, stems have been surrounded by pliable sleeves or sheaths. The stems are pulled out of the sleeves through a head portion of the rivet by a suitable tool while the rivet is held in place. When the rivet is pulled out, the pliable sleeve expands to lock the two structures in place. After the structures have been locked in place, the stems are generally broken off. When the stems are broken off from the rivet, small openings remain in the center of the heads of the rivet. These openings provide a problem in refrigerated trailers and it is this problem that the present invention is specifically directed to overcome.
When openings are left in the heads of the rivet as a result of the removal of the stem, bacteria and other germs tend to accumulate in the openings. Because of the side of the openings, it is extremely difficult to clean out these openings. In a case of refrigerated trailers involving food, it is essential that the interior of the trailer be free of germs and bacteria as must as is reasonably possible.